Mill grease



Patented Oct. 18, 1932 UNITED STATES PATENT OFFICE MAURICE H. ARVESON, OF HAMMOND, INDIANA, ASSIGNOB TO STANDARD OIL COM- PANY (INDIANA), OF CHICAGO, ILLINOIS, A CORPORATIONOF INDIANA HILL GREASE No Drawing.

This invention relates to a lubricant for use on open bearings at high temperatures, such a lubricant being commonly known as mill grease.

In cement mills, paper mills, etc. heavy machinery is equipped with open bearings which are lubricated by bricks of mill grease. These bearings usually operate at temperatures of 150250 F., sometimes higher, and the object of this invention is to provide such a mill grease that will withstand more severe operating conditions, higher temperatures and pressures, than greases heretofore known. A further object is to provide a grease of superior wearing qualities. A further object is to provide a process for making such greases which can be easily controlled and which will insure uniformity. A further object is to provide a more efficient process of making grease whereby the cost of manufacture may be reduced. Other objects will be apparent in the following description.

The invention contemplates an improved method wherein the sequence of steps, operating conditions and proportions of materials employed result in a grease of unusually smooth consistency, high melting point, great wearing resistance, and superior quality. A feature of the invention is the complete saponification of tallow or stearic acid prior to the addition of rosin-acid. Another feature is the unexpected abnormal wear resistance offered by a grease having about a one to one tallow-rosin proportion. Another feature is the regulation of the alkalinity by the addition of rosin oil subsequent to the saponification of the tallow. The invention will be better understood from the following detailed description of a preferred embodiment.

In preparing my improved mill grease I may use rosin, rosin oil, or other rosin-acid containing substance; tallow, stearic acid,

lard oil, cotton seed oil, oleo stearine, acidless tallow oil, or other fats or fatty acids; viscous hydrocarbon oils of various gravity, flash and viscosity characteristics; and alkalis such as sodium or potassium hydroxide.

Rosin-acid is preferably introduced as an 1930. Serial No. 448,178.

ingredient of rosin oil, which is obtained by digesting rosin in mineraloil at about 500 F. for about 42 hours, using about 30 parts of straw oil (84 second Saybolt at 100 F.) and 70'parts K rosin. The rosin oil prepared in this way contains about rosinacid.

. I may use the ingredients in about the following proportions:

26.2 partsby weight of rosin oil 12.2 parts by weight of tallow 59.0 parts by weight of oil (500 second Saybolt at 210 F.)

3.2 parts by weight of sodium hydroxide The rosin oil is next added, the heating and agitation being continued, and the tem perature is again raised to about 400 F. (37 5 to 450) to effect a reaction between the excess alkali and the rosin-acid.

Finally, .with continued heating and agitat-ion, the other half of the oil is added and the temperature is again brought to 400 F. (375 to 450 F.). The mixture should be neutral or slightly alkaline at this point and if the reaction is acid, a calculated amount of sodium hydroxide should be added. The grease is then ready to be poured into moulds. The mill grease prepared by this process is markedly different from and superior to greases formed by the usual process which consists in saponifying a mixture of fatty acid and "rosin. Instead of a grainy, soft, low melting composition I obtain a smooth, clear,

hard, elastic, high melting mill grease that shows unprecedent wear resistance.

Tests with different rosin-tallow mixtures disclose an unexpected peak in consistency curves. If IOSlIl Oll 1s used, this peak occurs when the amount of rosin oil is a little more than twice the amount of tallow by weight rosin. Greases made withrosin show substantially the same characteristics as those made with rosin oil, the latter however, at peak consistency shows a lower consumption at 250 to 260 F. and a better top bearing temperature (the temperature at which the last trace of grease leaves the bearing cup). The top bearing temperature for a rosin grease was 330 F. while that of the corresponding rosin oil grease was about 360 F. (within 5 of its melting point).

I believe that an important feature of my invention is the complete saponification of the tallow by the sodium hydroxide prior to the addition of the rosin, the rosin being used to clean up the excess sodium hydroxide and to thereby regulate the alkalinity. I do not limit myself to any theory to account for my phenominal results, but they are probably due to more complete saponification of fatty acid, less complete saponification of rosinacid and/or the treatment in at least two distinct steps as hereina'bovepointed out.

YVhile I have described in detail a preferred embodiment of my invention, it is understood that I do not limit myself to these details except as defined by the'following claims.

I claim:

1. A method of making grease which comprises saponifying a fatty acid with an excess of alkali and subsequently adding a rosinacid to neutralize the resulting alkalinity.

2. A method of making grease which comprises treating a fatty acid with an excess of alkali at a temperature of from 375 to 450 F., subsequently adding a rosin-acid thereto, and heating the resulting mixture to a temperature of 37 5 to 450 F.

3. The process of making a grease which comprises completely saponifying a fatty acid with an excess of alkali and subsequently adding a rosin-acid to utilize the remainin V alkali, both steps being carried out in the presence of oil.

4. The comprises sequently process of making grease which saponifying a fatty acid and subsaponifving rosin-acid, the total alkali for the sa'ponification being added to the fatty acid and the saponification thereof being substantially complete before the rosin acid is added to the mixture.

5. The process of making grease which comprises adding to a fatty acid a quantity of alkali suflicient to saponifysaid acid and a 8. The process I of' making grease which comprises digesting rosin 1n oilto form IOSlIl oil, and adding said rosin oil to substantially neutralize an alkaline mixture of saponified fatty-acid in oil.

Signed this 21st day of April, 1930, at Whiting, in the county of Lake, State of Indiana.

MAURICE H. ARVESON. 

